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Mix of result and applicative
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| module Result = | |
| let bind f = function | |
| | Ok x -> f x | |
| | Error x -> Error x | |
| let map f = function | |
| | Ok x -> Ok(f x) | |
| | Error err -> Error err | |
| let apply fResult xResult = | |
| match fResult, xResult with | |
| | Ok f, Ok x -> Ok(f x) | |
| | Ok _, Error x -> Error x | |
| | Error f, Ok _ -> Error f | |
| | Error f, Error x -> Error(List.concat [ f; x ]) | |
| let mapError f = function | |
| | Ok success -> Ok success | |
| | Error failure -> Error (f failure) | |
| let (>>=) m f = Result.bind f m | |
| let (<!>) = Result.map | |
| let (<*>) = Result.apply | |
| /// mix of monad and applicative | |
| type Username = Username of string | |
| module Username = | |
| let create u = | |
| if String.length u > 10 | |
| then Error ["Too long"] | |
| else Ok (Username u) | |
| let value (Username s) = s | |
| type Email = Email of string | |
| module Email = | |
| let create s = | |
| if String.length s > 10 | |
| then Error ["Wrong email"] | |
| else Ok (Email s) | |
| let value (Email s) = s | |
| let login u e = | |
| let (Username u) = u | |
| let (Email e) = e | |
| [|u; e|] |> String.concat "-" | |
| type ResultBuilder() = | |
| //member this.Return(x) = Ok x | |
| member this.Bind(m, f) = Result.bind f m | |
| member this.Zero() = None | |
| member this.Return(x) = Ok x | |
| let result = new ResultBuilder() | |
| let xx = result { | |
| let! l = | |
| login | |
| <!> (Username.create "12345678900") | |
| <*> (Email.create "12345678900") | |
| let! u = Username.create "abc" | |
| return u | |
| } |
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